Subject of the invention is an improved double lumen catheter for a device for the in-vivo purification of blood in which blood pumped out of a vein is subjected to intensive ultrafiltration and the retentate together with a quantity of substitute fluid roughly corresponding, volumetrically, to the filtrate is reintroduced to the vein. The device is particularly suited to filter out agents introduced in high concentration, in intra-arterial chemotherapy, before the venous blood reaches the heart and subsequently the circulatory system of the body.
Ultrafiltration of human blood in case of kidney failure to bring about a substitute function of the liver, is known. In this process blood is taken from an artery and, under its own pressure, passed through an ultrafilter or a so-called hemofilter, and the retentate is reintroduced, if desired together with a substitute fluid, into a vein. Pumps have also been interposed where the withdrawal and the reintroduction of blood are to be carried out from a single blood vessel.
In order to make this possible numerous double lumen catheters have been developed.
In German patent application DE-OS 3,010,841 a double cather has been described the catheter tubes of which are formed to be slidable with respect to each other and which can be used for the vein puncture for hemodialysis. Because of the slidability of the individual catheters the inlet openings or the outlet opening of the individual catheters can be placed at their tips, upon insertion into a blood vessel, in such a spacing with respect to each other that the blood reintroduced into the blood vessel does not reach the range of the withdrawal location.
From European application EP-OS 0 025 704 a double lumen catheter is known the lumens of which are formed to be coaxially slidable relative to each other so that only one portion needs to be introduced into the blood vessel. The inner lumen may be replaced without the necessity of withdrawing the outer lumen having the larger diameter from the blood vessel. The catheter tip is open and along the catheter there are provided, in addition, several lateral openings which with the two lumens, make simultaneous withdrawal and reintroduction of blood possible.
In French patent specification FR-PS 2 297 640 a double lumen catheter has been described in which one of the catheter tubes is enlarged to form a balloon. The balloon which consists of an elastic material is enlarged by the pressure of the reintroduced liquid to such an extent that it contacts the wall of the vessel and blocks the flow: The withdrawal location in front of the balloon is spatially separated in this fashion from the reintroduction location which lies behind the balloon. This design has the decided disadvantage that the blood vessel is completely blocked so that an undesired back pressure is produced and that also in the reintroduction of the blood from the second catheter tube into the vessel, an inhomogeneous flow profile is created.
In German patent application P 32 28 438 a double lumen catheter has been described.
In this catheter the first catheter part has a closed tip and a plurality of openings laterally provided in the vicinity of the tip. The second catheter lumen is located in the first and it terminates, with two or more openings, in the outer wall of the first catheter tube. The distance between the lateral opening of the first catheter tube farthest removed from the catheter tip and the nearest opening of the second catheter tube is 40-50 mm. The end openings of the second catheter tube in the wall of the first catheter tube are as large as the cross-section of the second tube.
A number of disadvantages have shown up in using this catheter in the in-vivo purification of blood. In this technique the catheter is used in combination with a hose from the first catheter part connected by way of an interposed first hose pump with the input side of an ultrafiltration filter; a second hose connecting the output side of the ultrafiltration filter with the second catheter lumen for the reintroduction of the retentate; a supply line, with an inserted second hose pump, for substitute fluid terminating in the hose line behind the filter; a supply line for anticoagulants terminating in the hose line before the filter; and an outlet line for the filtrate from the ultrafiltration filter terminating by way of a precisely adjustable valve in a measuring container.
These disadvantages, in particular, are in the nature of manufacturing difficulties relating to the coaxial arrangement of the catheter tubes and the reliable fitting of the ends of the inner lumen into openings of the outer wall of the second, outer lumen. It has also been found that the conditions applying to the inflow through the lateral openings in the vicinity of the catheter tip upon introduction of the catheter into the vena cava in immediate proximity to the heart, are still subject to improvement if, in intra-arterial chemotherapy, especially in tumor treatment the suitable chemotherapeutics are applied to the desired treatment location in as high a concentration as possible and, downstream of the treatment location, have to be filtered out again from the venous blood of the vena cava in order to avoid toxic effects and side reactions downstream of the treatment location.